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International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 1 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
Conservation and Restoration Research on 2nd
BCE Murals of Ajanta
M.Singh1*
and B.R.Arbad2*
Abstract
This paper outlines new approach for the removal of varnish coatings from the surface of wall paintings.
Covered under very thick layers of different kinds of varnishes applied in the past for copying, the few sq.mt. 2nd BCE
painted plaster still surviving in cave no 9 and 10, Ajanta pose most difficult task of cleaning the historic surfaces. The
paintings diagnosed to be executed on a very thin lime plaster ground with inorganic colors by portable XRF; the FTIR
spectra of the pigments and lime ground denote that varnishes have seeped through due to its repeated application in the
past. The usual organic solvents mixture technique being used as well as the micro-emulsion technique applied for
cleaning proved non-effective in the treatment of that part of the paintings covered with thick bats excreta. Microclimatic
condition and state of conservation of painted plasters are also discussed.
Introduction:
One of the biggest challenges in the
cleaning of the painting is the removal of substances
from the surface of the painting having chemical
composition quite different to the original material1. In
the past many different kinds of varnishes such as
shellac, copal, mastic, polyvinyl acetate etc. have been
widely used as consolidant or protective coating for the
conservation of wall paintings. At Ajanta, many of
these varnishes found to be applied repeatedly in cave
no 9 and 10 (2nd BCE) for the purpose of copying the
paintings in 19th century by various artists ever since its
discovery in the year 1819.
The Japanese copyist of 1916 Mr. Kampo Arai wrote
about the condition of paintings during copying,
“When British conducted their reproduction activity,
they covered entire wall surface with varnish which
made the surface greasy and rather unpleasant
appearance and changed colour of the paintings from
the original”. Finally, the Italian conservators of Ajanta
paintings applied shellac varnish as preservative on
painted surface without removing the earlier varnish
coats in the year 1920. Moreover, looking towards the
history of scientific cleaning of the painted surface in
India, it is observed that acrylic polymers are still being
used as consolidant and protective coating. It is also
observed that in certain instances following removal of
acrylic polymers from the painted surface, the same
materials was subsequently applied as protective coat
to the painting2.
The most serious problems associated with all these
materials are related to change in their physico-
chemical property due to their natural aging3. Thermal
and photo-chemical reaction of these materials alter the
colour and physical appearance of the surface, causing
mechanical stress to the paint layers that lead to
formation of cracks, ridges, gaps, lacuna etc on the
painted surface4. They also result in the alteration of
physico-chemical property at the interface between the
work of art and its environment. One of the main
1 Archaeological Survey of India, Science Branch, Western Zone,
Aurangabad-431004 2 Department of Chemistry, Dr.Babasaheb Ambedkar
Marathwada University, Aurangabad-431004)
*For correspondence (e-mail:[email protected] or
International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 2 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
consequences of polymeric degradation of these
materials is the drastic loss of their solubility3 which
makes their removal much more difficult by using
conventional mixed solvent system for cleaning the
painted surface presently being applied at Ajanta. It is
also noticed that reversibility of previous coating with
polymer is reduced with time.
Since the conservation of historic surface can often
cause chromatic alteration, it is essential to minimize
this impact through the development of new
conservation methods and materials or improvement
of those already in use. Hence, one of the biggest
challenges the conservators face is the removal of
substance that have a different chemical composition
from the original materials. The complete removal of
these materials is often a delicate problem due to
heterogeneous and porous nature of the support. The
use of organic solvent mixture on porous surface for
cleaning can also result in the partial redistribution of
the unwanted substances through the porous ground.
The frequent appearance of chalkiness on the cleaned
surface of cave no. 17 murals at Ajanta is attributed to
this factor5. However, controlled cleaning with the
minimum use of same solvent mixtures have not
produced any chalkiness over a period of 15 years
during the cleaning work of many square meters of
painted surface in various cave at Ajanta6. A solution
to this problem can also be found by using micro-
emulsion in which the dispersed solvent phase is
specifically tailored to solublize the substance that are
to be removed7. The micro-emulsion is stabilized by
the surfactants which have polar and non-polar group.
With this the environmental impact of previous
treatment technique is drastically reduced in closed
cave interiors8. The re-distribution of the solublized
material into the porous ground is avoided since the
solublization takes place within the core of the micro
droplets. This system is also stable throughout the
wide range of environmental operating conditions.
Both these techniques were
successfully employed in the cleaning of few sq. meters
of painted surface in cave no 10 left wall by the side of
stupa at Ajanta. However, the techniques could not
produce any result during the cleaning operation of
some other painted plaster within the same panel
which were found badly infested with bats excreta and
totally dried out. These papers outlines the techniques
employed and stress the need for finding newer
methodology for cleaning painted surface having thick
bat excreta that has seeped through the porous surface
into the interior of the painted plaster. Large parts of
bats droppings have also made the upper part of the
painted plaster illegible.
General condition of the cave 10, Ajanta
One of the major reasons for damage
to the paintings at Ajanta is the roosting of bats in the
corner and dark part of the cave interiors ever since
these caves were abandoned in 6th A.D by Buddhist
monks. During this period the façade have fallen, the
pillar, support and walls in the many caves also fell and
in some caves the rain water which is supposed to flow
into the ravine of Waghura River has entered inside the
cave. Photograph (1A) shows the condition of the cave
no 10 in 19th century when muddy water flowed inside
the cave causing damage to the structure and paintings
up to 4-5 feet from the floor level of the cave. In the long
run this has also caused crumbling and falling of pillars,
wooden rafters etc. into the cave interior. Major
structural conservation measures were taken in the form
of removing the filth from the cave interior and making
new support pillars as per requirements, photo (1B).
International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 3 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
Photo 1A- Showing Cave no 10 in 19th Century.
Photo 1B- Showing Cave no 10 at Present.
As the cave no 10 has the largest opening at Ajanta,
wire mesh in wooden frame were fitted so as not to
allow any bats/birds to enter inside the cave. A few
square meters of painting belonging to 2nd BCE that
survived on both side walls of cave no 10, were also
damaged by visitors graffiti. To save the paintings from
graffiti, it was caged under glass on both the side wall.
However, 3-4 sq.mt. 2nd BCE painting surviving on the
left side wall by the side of the stupa above 8 feet from
the floor of the cave were left as such without any cover.
As the painting work were executed by the side of the
stupa behind the pillars, the place is always dark
compared to front portion and on this part of the
paintings much bat excreta are noticed. Atmospheric
condition of the cave has dried the excreta into a
compact mass within the painted surface. Figure- 2
shows the plan of the cave no. 10 Ajanta with area
marked where conservation treatment was carried out.
Figure- 2 showing ground plan of cave no 10, Ajanta
Outlines of the painted surface
As this part of the paintings were
repeatedly applied with varnish coating for copying
under the light of oil lamp in 19th century, the whole
painted figure were totally covered under varnish
layers accompanied with dirt, dust, smoke etc. Large
expanses of bats dropping have made the painted
surface further illegible by naked eye. Before
undertaking any cleaning operation, it is essential to
have at least a primary knowledge about the design and
shape of the painted figures for ease in treatment. The
panel painting was observed under an adjustable
illuminated magnifier. The paintings were observed by
this process though the thick layer of varnishes. Figure-
3 shows the original condition of painted plaster and
outlines drawn after examining the painted surface
through thick varnish layer under magnifying lenses.
As from the outside no figures are visible to naked eye
due to thick varnish coats, the outlines helped the
conservators in planning the conservation operation.
Figure-3 showing the original painted plaster and its
outlines.
IR image of the painted surface
The painted surface was also observed
under infra red light to visualize the painted surface
and its condition. Figure-4 shows the view of the
painting under IR light source. The outlines of the
figures are very clearly visible under the IR light which
is very thin and sharp, an essential characteristic of 2nd
BCE painting. The missing part of the painting can now
be easily seen. The bat excreta and soluble salts
accretions over the painted surface is clearly visible.
This has clearly given primary information about the
painted figures, varnish layers and accretions present on
the historic surfaces.
Murals taken for treatment
International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 4 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
Figure-4 showing painting under IR light source
XRF Analysis:-
Pigment analysis using portable
energy dispersive X-ray fluorescence (ED-XRF) was
carried out in this cave along with Italian conservation
team9. The technique identifies the elements present
and not the compounds that make up the materials
under study. This limitation cannot be considered a
handicap as it is possible to establish the pigments from
the presence of particular elements, associated with the
colour analysed.
As already reported10 the most ancient 2nd BCE
paintings of cave no. 10 is executed on lime plaster
ground on a basaltic rock support which has been
chiseled into a smooth surface. As compared to other
2nd BCE painting existing in cave 10, the pigment and
plaster layer thickness of the panel painting under
question is very thin. The approximate thickness of
various layer are: - Lime
plasters layer ~0.5 mm
Pigment
Layer <0.5 mm
Varnish layer (uneven) ~0.5 to 1 mm
The lime plaster was found applied in one
layer, the outer surface of which was smoothened to
receive the colors. As obtaining sample of sufficient size
is a major problem in this case, it was proposed to apply
non-destructive technique to get information about the
composition of support and pigments applied in this
cave painting. Portable XRF was used for this purpose
and the data obtained is shown in table-1 for lime, mud
&pigment layers of cave 10, Ajanta.
Table-1 Showing data for lime, mud &pigment layers,
cave no 10, Ajanta.
Sr.no. Colour Description
ca Fe As pb Sr.
1 Brown-red figure
115 101 900 - 18
2 Yellow figure
136 96 99 - -
3 White figure 88
70 850 - 18
4 White lime plaster
51 30
5 Grey mud plaster in
41 173
Arch (Thin
layer)
6 Grey mud plaster in
33 113
Arch (Thick layer)
The data indicates that pigments used in 2nd
BCE paintings are inorganic in nature mostly yellow
ochre or orpiment for yellow, red-ochre or realgar for
red and lime for white. The 2nd BCE paintings on both
the side walls have been executed on a thin lime plaster
ground whereas the paintings in the arch of the same
cave have been executed on grey colour mud plaster
containing ferruginous earth and pertains to the period
of 3-4th A.D since it is of different artistic significance
than the 2nd BCE paintings. It was also observed that
stone surface in the arch is very rough so as to receive
and hold the mud plaster layer. In contrast the side
walls of the cave have been smoothened as the lime
plaster can easily hold to such surface.
FTIR images of pigments and plaster:-
Few grains of pigment and lime plaster
support from the panel were observed under FTIR
spectroscopy. Figure-5 shows the FTIR image of lime
support. The main functional group observed are FTIR cm-
13404 (phenolic OH), 1620(NH), 1392(NO2) (C-N of amine),
781 (phenyl). From the above it is clear that the sample
contains various groups like phenol, amine, nitro & alkenes
which are the major component of copal, mastic or shellac
International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 5 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
varnishes. From this, it can be claimed that during the process
of copying the paintings in 19th century the varnishes have
seeped into the lime layer since as per record the paintings
were never been cleaned so for.
Figure-5 showing FTIR image of lime support Cave no 10
FTIR image of pigment grain is shown in figure 6.
The main functional group identified through FTIR spectra
are 3043(phenolic OH), 1619(NH), 1390(NO2), 1112 (C-N of
amine), 779 (phenyl).From this, it is clear that the sample
contains various groups like phenol, amine, nitro &alkenes
which are the major component of copal, mastic or shellac
varnishes. As the pigment layer is the outer layer of the
painting, the intensity of the groups in the spectra of pigment
is more as compared to the intensity to the lime spectra. From
the above studies it can be claimed that varnishes have seeped
through the painted layer into lime support.
Figure- 6 Showing FTIR image of pigment grain Cave no
10.
Microclimatic condition of the cave:-
Cave no. 10 has one of the widest open door arches at
Ajanta which is about 75 feet in height and 40 feet in
width. The door arch is fitted with iron mesh in
wooden frame, the upper part of which is closed with
tinted glass leaving about 10 feet height from the floor
all along the width for air circulation through iron
mesh. This has inhibited entering of birds and insects
into the cave interior. The basaltic rock on the outside of
cave no 10 get heated up considerably in sunny days
and heat radiation enters the cave with wind through
the opening of wire mesh
International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 6 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
Figure-7 shows the surface temperature of basalt rock
both in the sun lighted area and shadow area. As cave
no 10 does not have any porch to stabilize temperature
/humidity as in cave no 1, 2,11,16,17 etc. at Ajanta, there
is a direct bearing of these parameters inside the cave11.
The comparison of data recorded using the data logger
and spot measurement for measuring temperature and
humidity in the case of cave no 17 was found highly
satisfactory and confirms the suitability of both the
methods of measurement. Spot measurement of
temperature and humidity both inside (near the center
of the cave) and outside shadow area of cave no. 10
Ajanta was carried out from 10.02.2007 to 31.10.2007.
Figure 8 and 9 show data for temperature and humidity
both inside and outside cave 10 Ajanta.
From the graph it is observed that the temperature
inside the cave is approximately in consonance with the
temperature in shadow area outside the cave as
difference noticed is about 1 to 1.5oC. From the
hygrometric graph, it is also observed that inner part of
the cave is just 2 to 3% more humid than to the one
under shadow area outside the cave. This is only due to
reason of wide opening of this cave through which air
circulation is possible thus the atmospheric condition of
cave no 10 is quite in contrast to other caves at Ajanta.
It is also observed that drop in humidity inside the cave
are closely related to the humidity outside due to proper
circulation of air and absence of any porch. In order to
better assess possible spatial gradients linked to the
shape of the cave and the distribution of visitors, grid
survey was carried out. The result has, however
marked homogeneity in the temperature and humidity
values. The maximum variation in temperature and
humidity is noticed near the entrance door. The
maximum spatial thermal gradient is around 0.5oC and
hygrometric variation of 1% noticed inside the cave.
The temperature is always above 25oC and this confirms
low probability of condensation on the painted surface
and moisture content level on the painted wall.
Methodology for conservation
The panel painting was brushed very
softly for the removal of adhering dust, dirt, etc. from
the surface followed by general cleaning with ethyl
alcohol with the help of cotton swab. Many gaps,
lacuna, cracks etc. noticed on the painted surface were
fixed by slowly injecting lime plus casein mixture and
pressing the surface with rubber roller. The painted
surface was left as such for about 2 months for proper
consolidation of loose and defective parts.
For scientific cleaning of the paintings
two different technique were applied. In the first
technique, the mixture of organic solvents, two
component system as described elsewhere10 was used
to clean the surface with the help of cotton buds. In this
process, it was ensured that the minimum quantity of
cleaning solvent mixture was used for removing
accerationary deposits of varnishes, dust, dirt, smoke
etc. without giving any chance for the chemical mixture
to seep into the ground of painting. The process is very
delicate and exclusively depends on the dexterity and
precision of the conservators. As the pigment layer in
this panel is too thin, during cleaning operation it was
not possible to reach up to the pigment surface with
human eye due to great fear of losing any grain of
pigment during the process of chemical treatment.
Hence, the cleaning operation was carried out for
superficial removal of 75-80% of varnish layer leaving
20-25% margin for cleaning by other sophisticated
technique in future. The main purpose of the treatment
was to reduce the thickness of varnish layer to render
International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 7 ISSN 2229-5518
IJSER © 2012
http://www.ijser.org
the underlying surface to breath. Highest dexterity and
precision was taken during the operation and figure-10
shows the before/after conservation work of the
painting executed through this technique.
Figure-10 showing before/after conservation
photographs Cave no 10, Ajanta.
As the solvent mixtures applied in the
above technique are slightly harmful for conservators, it
was proposed to replace it with micro-emulsion
technique. For this 1.0 gm of citric acid was dissolved
in100 ml of deionized water. This solution is added into
1.5 gm of carbopole (polyarcylic acid) with constant
stirring followed by addition of 5.0ml of
triethanolamine drop wise with stirring. This will form
a gel namely solvent-gel chelante. For cleaning the
painted surface following solutions were also prepared.
A. Petroleum spirit- 15ml B. Acetone- 1ml
C. Dimethyl sulphoxide- 25ml
Dimethyl sulphoxide-5ml Ethyl alcohol-
4 ml. Ethyl acetate- 50ml
Isobutyl ketone- 25ml
D. Dimethyl sulphoxide- 1 part E. Dimethyl
sulphoxide 60 ml (pH adjusted to about 8.5 using
ammonia)
Ethyl acetate- 1part Isobutyl ketone
40 ml
On the specific area, the Japanese tissue paper
is stick with the appropriate concerned solution. The
solvent gel chelante and concerned solution mixed
properly is applied on Japanese tissue paper with fine
brushes very gently. The solution is spread equally on
the tissue paper and kept for 5, 10, 15 & 20 minutes as
per thickness of the varnish layers. After this the tissue
paper was removed and the surface cleaned slowly with
concerned solution with vey soft brush with great
precision and dexterity. Again precaution was taken
not to reach up to the pigment layer and 15-20% of
varnishes were left as such due to fear of losing any
grain of pigment layer. Figure -11 shows the painting
cleaned by this technique in this panel. All the chemicals
used in the cleaning are the AR grade chemicals as
supplied by the firm.
Figure-11 showing before/after conservation
Photographs Cave no 10, Ajanta.
As we moved little inner in the same
panel, it was noticed that the painted surface has
suffered due to hard and dried bats excreta. Attempt to
clean the surface with both the above technique proved
futile. As many part of the painting in the inner area
and corner are infested with bats excreta in Ajanta cave,
there is need for proper research to find exact
methodology for cleaning such historic surfaces.
Acknowledgement
We thank The Director General and the
Director science, Archaeological Survey of India for help
and support extended for this work. The help extended
by Shri. R.S.Trambake, Project Modeller, Shri. A.S.Patil,
Asst.Archl.chemist, and Shri. N.E.Mahajan,
Photographer Ajanta is gratefully acknowledged.
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International Journal of Scientific & Engineering Research, Volume 3, Issue 10, October-2012 8 ISSN 2229-5518
IJSER © 2012
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